It has been found that positive pressure ventilation of structures sustaining an internal fire has many advantages. Positive pressure ventilation techniques are used to quickly remove smoke from the area to reduce smoke damage. Perhaps more importantly, the rapid removal of smoke and cooling of the inflamed area dramatically increases fire fighting safety. Firemen entering the structure will have considerably greater visibility and are more able to rapidly locate hot spots without having to crawl on the floor. Speedy removal of smoke and the replacement with cool air allows breathing apparatus to be removed earlier. Overall physical stress of fire fighters is reduced with fewer stress related injuries. This all results in greater fire fighting productivity.
To be able to obtain the above advantages, lightweight portable positive pressure blowers have been developed that may be easily maneuvered into position in front of an opening to a burning structure. Such a blower is disclosed in U.S. Pat. No. 4,906,164. The blower disclosed therein has substantial benefits in producing a positive ventilating pressure for fire fighting. The disclosed blower is easily transported and stored on a fire fighting vehicle. However, the adjustment capability for the blower is a relatively complex mechanism and is situated toward the ground surface. A hand crank is provided to change the angular position of the blower by pivoting forward legs that are provided independently of rearward, rigid supporting legs. The engine, propeller, and housing are connected rigidly to the rearward legs while the forward legs pivot to change the angular orientation of the blower. By pivoting the forward legs, the "foot print" of the ground engaging pads changes. As the angular position of the blower increases from the horizontal, the longitudinal spacing between the forward and rearward "feet" becomes shorter.
U.S. Pat. No. 5,062,487 discloses a similar blower arrangement and frame structure but with the provision of nozzles for connection to a source of water under pressure. The nozzles introduce a mist of water in the airstream to obtain additional benefits in cooling in moistening the air moving toward the "hot spots".
A misting fire ventilation blower is commercially available through the Hale Fire Pump Company of Conshohocken, Pa. The device is sold under the trademark, "TYPHOON". It includes a water turbine driven positive pressure ventilation system with an on demand water mist injector. The blower, turbine, blade, and housing is pivoted on a supporting frame. The pivot axis from the frame passes substantially through the center of the motor. The elevation from the ground or supporting surface to the pivot axis represents a substantial moment arm against which the thrust from the fan operates.
Other blower arrangements have been provided in which the blowers pivot about axes transverse to the blower fan blade rotation axes. The pivot axes are positioned at substantial elevations in relation to the ground surface. Thrust from the blowers has a tendency to render the blowers unstable, and vibration from the driving motors or engines plus the thrust from the fans cause the blowers to "walk" or move about during use.
The fans of prior blowers used for producing positive ventilation air pressure typically develop a narrow cone shaped airflow, due to the conventional shape of the fan or propeller blades. It has been found desirable to seal the air passageway with positive air pressure to avoid undesired and unpredictable exchange of air from within the affected structure through the air entry opening (usually a doorway or window). To create the "seal" prior blowers were positioned far enough from the structure that the air flow cone produced would be large enough at the entry to span the opening and effect the desired seal. This seemingly effective solution is not without drawbacks. An airstream will loose much of its energy and dissipate over distance. The airstream is thus diminished at the critical area within the structure.
A need therefore remains for a positive pressure ventilation blower that can be placed close to an opening yet that will both effect a "seal" about the entry and that will deliver a strong, effective current of air to the desired area within the structure. There is further need for a blower that is compact and in which provisions are made to absorb the forms of vibrational energy which have the tendency to cause other forms of blowers to "walk" or move about during operation, especially on wet or icy support surfaces.
One of the objects of the present invention is therefore to provide a compact, hand portable positive pressure blower that can be easily stored on a fire fighting vehicle, that will be stable in use and that will not have a tendency to "walk" due to thrust and vibration.
Another object is to provide such a blower that has capability to produce a wide cone airstream at close proximity to the propeller thereof.
A further object is to provide such a blower in which angular adjustment of the airstream is achieved quickly and easily.
A still further object is to provide such a blower that includes a supporting framework that will protect both the propeller blade and the engine during transport and use.
These and still further objects and advantages will become apparent upon reading the following description which, taken with the accompanying drawings, describe a preferred form of the present invention.